Multi-layer golf ball

ABSTRACT

The present invention relates to a golf ball that provides improved playing characteristics by providing a cushioning interface between a center and subsequent layers. The ball can include a center, a soft intermediate layer, and a cover, although various constructions and modifications are possible. The intermediate layer can include an elastomeric latex or solution that will dry to form a soft film on the surface of the center. Such a soft rubber interlayer can serve as a cushioning interface to help improve durability and softness of the ball upon club impact. In another embodiment, the thin intermediate layer includes a responsive viscoelastic composition that exhibits an increase in viscosity under shear forces.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of application Ser.No. 09/243,455, filed Feb. 3, 1999, now pending, the disclosure of whichis incorporated herein by express reference thereto.

FIELD OF THE INVENTION

[0002] The present invention relates to a multi-layer golf ball andmethods for forming a portion thereof including a core having a centerwith at least one center layer, a mantle having at least one mantlelayer of a resilient polymer component disposed concentrically about thecenter, a soft, thin intermediate layer disposed preferably between thecenter and the mantle, and at least one cover layer disposedconcentrically adjacent the core. The invention also relates to thepolymeric composition used in forming the intermediate layer. In anotherembodiment, the thin intermediate layer includes a responsiveviscoelastic composition that exhibits an increase in viscosity undershear forces.

BACKGROUND OF THE INVENTION

[0003] Generally, golf balls have been classified as solid balls orwound balls. Solid balls are generally comprised of a solid polymericcore and a cover. These balls are generally easy to manufacture, but areregarded as having limited playing characteristics. Wound balls arecomprised of a solid or liquid filled center surrounded by tensionedelastomeric material and a cover. Wound balls generally have a goodplaying characteristics, but are more difficult to manufacture thansolid balls.

[0004] The prior art is comprised of various golf balls that have beendesigned to provide optimal playing characteristics. Thesecharacteristics are generally the initial velocity and spin of the golfball, which can be optimized for various players. For instance, certainplayers prefer to play a ball that has a high spin rate for playability.Other players prefer to play a ball that has a low spin rate to maximizedistance. However, these balls tend to be hard feeling and difficult tocontrol around the greens. Therefore, attempts to create a golf ballthat couples the production ease of a solid ball with the beneficialplaying characteristics of a wound ball, have been numerous.

[0005] A Japanese Publication No. 10127819 is directed towards a methodfor constructing a solid golf ball that provides a “soft” ball-hittingtouch. The golf ball consists of a solid core of a three layer structurecomprising an internal layer, an intermediate layer, and a cover layer,and a cover over the solid core. The internal layer of the three-layerstructure is set to a JIS-C hardness of 40-90, the intermediate layer ismade up of a thermoplastic resin composition to be set to a JIS-Chardness of 50-80, and the cover layer is set to a JIS-C hardness of 65or more.

[0006] Another reference, U.S. Pat. No. 5,184,828 discloses a dual coregolf ball whose core has a maximum hardness at the surface of the innercore and then increases in hardness from the surface of the inner coreto the center of the inner core and from the surface of the inner corethrough the body of the outer core. Specific hardness ranges for eachlocation are specified but the patent does not address the use of softelastomeric film between layers.

[0007] Similarly, Japanese Patent Application No. 8-322964A of KascoCorporation discloses a dual core ball whose core has an increasinghardness gradient, requiring that the inner surface of the outer core beharder than the remainder of the outer core.

[0008] The prior art additionally discloses a number of methods for themanufacture of golf balls employing a soft elastomeric film (such as alatex dip) on wound constructions. U.S. Pat. No. 5,733,428 discloses theuse of latex dips within the body of a wound core to produce multilayerwound cores. The prior art also discloses the concept of a coatingbetween the core and the outer cover of the ball; the coatings werecomprised of fully-cured epoxy or other adhesive material to helpincrease core to cover adhesion.

[0009] However, none of these patents disclose or even suggest anonwound, dual, multicore or liquid-center ball having the materials andmaterial property requirements as disclosed herein, specifically the useof a soft, intermediate layer between the inner sphere and subsequentmantle layers, to provide the improved balls of the present invention.The softer, rubber interlayer can serve as a cushioning interface toimprove the overall softness of the ball, as well as the fracturedurability.

SUMMARY OF THE INVENTION

[0010] The present invention relates to a golf ball, and moreparticularly golf balls that have a multilayer core that providesimproved playing characteristics by providing a cushioning interfacebetween the center and any subsequent layers. The ball is comprised of acenter; a soft, thin, elastomer latex intermediate layer around thecenter wherein the intermediate layer is less than about 0.01 inchesthick and has a flexural modulus of less than about 10,000 psi; one ormore mantle layers disposed concentrically adjacent the intermediatelayer, wherein the mantle layer material comprises a resilient polymercomponent; and a cover layer disposed concentrically around the mantle.

[0011] Any soft, elastomeric latex or solution that will dry to form asoft film on the surface of the center or other subsequent mantlelayers, can be employed as the intermediate layer. Typical thermosettinglatex materials which can be used to coat the cores include low ammonianatural latex and/or pre-vulcanized natural latex. Natural latex isnoted for its combination of high tensile strength, excellentelasticity, tack, low modulus, and ability to form strong, coherent, wetand dry films. Natural rubber latex is also relatively inert, nontoxic,cost effective, compatible with most core and outer shell rubbercompounds, and can be air dried.

[0012] A preferred latex material is a partially pre-vulcanized naturallatex that can be diluted with water to any solid content. It isunderstood that non-latex encapsulating materials may also be used. Suchmaterials include elastomer adhesives as well as aqueous and non-aqueousadhesives, urethane dispersions, synthetic latexes, and alkyd resins.Other materials that could be suitable for the soft, intermediate layer,include aqueous acrylic and latex copolymers, and polyurethane coatingsand preparations. The soft intermediate layer may also containadditives, fillers, thickeners, or a combination thereof, to adjust thespecific gravity of the layer to alter various golf ball properties asneeded or desired.

[0013] A natural rubber latex, when dried, is softer than either theinner or outer core compounds conventionally employed in golf ballmanufacture. This property is particularly evident when the inner andouter core compounds are crosslinked and the latex is not. A soft rubberinterlayer can serve as a cushioning interface to help improvedurability and softness of the ball upon club impact. A soft rubberinterlayer also serves to improve fracture durability, particularly whena strong adhesion between the center and mantle layers does not exist.In one embodiment of the present invention, the intermediate layerthickness is from about 0.0005 to 0.01 inches. Preferably, theintermediate layer thickness is from about 0.0008 to 0.01 inches. Inanother embodiment, the intermediate layer has a Shore A hardness ofless than about 90. In a preferred embodiment, the intermediate layerhas a Shore A hardness of less than about 70. Alternatively, theflexural modulus of the intermediate layer is less than about 3,000 psi.

[0014] The inner sphere, or center, may be of any dimension orcomposition, such as a thermoset solid rubber sphere, a thermoplasticsolid sphere, wood, cork, metal, or any material known to one skilled inthe art of ball manufacture. Preferably, the solid inner sphere iscomprised of a resilient polymer such as polybutadiene, natural rubber,polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber.Similarly, the inner sphere could be a fluid-filled sphere such as arubber sack, a thermoplastic, or metallic shell design, in which thefluid could be of any composition or viscosity available to those ofordinary skill in the art. It is also feasible to construct such acenter with a void or gas center. In one embodiment, the center has anouter diameter of about 0.5 to 1.50 inches. Preferably, the center outerdiameter is about 0.75 to 1.25 inches. In another embodiment, thecombination of the center, the soft elastic intermediate layer, and themantle has an outer diameter of about 1.45 to 1.6 inches. Preferably,the combination of the center, the soft elastic intermediate layer, andthe mantle has an outer diameter of about 1.5 to 1.58 inches. In anotherembodiment, the center can be filled with a fluid such as a liquid or agas, a gel, or a cellular foam.

[0015] In still another embodiment, the intermediate layer is comprisedof low ammonia natural latex and/or pre-vulcanized natural latex,elastomer adhesives, synthetic latexes, acrylic esters, alkyd resins, ormixtures thereof. Preferably, the soft intermediate layer is comprisedof a natural or a synthetic latex.

[0016] In the current invention, a mantle comprising at least one layer,the layer comprising a resilient polymer component, is disposedconcentrically around the intermediate layer. The mantle layer maycontain a reinforcing polymer. Reinforcing polymer components, such astranspolyisoprene, block copolymer ether/ester, acrylic polyol, apolyethylene, a polyethylene copolymer, 1,2-polybutadiene(syndiotactic), ethylene-vinyl acetate copolymer, cyclooctene,trans-polybutadiene, and mixtures thereof, should have a glasstransition temperature sufficiently low enough to avoid causingcrosslinking or thermal degradation of the resilient polymer.Alternatively, the resilient polymer component of the mantle layercomprises polybutadiene, natural rubber, polyisoprene,styrene-butadiene, or styrene-propylene-diene rubber, or a mixturethereof. In one embodiment, the resilient polymer component of the solidcenter comprises polybutadiene, natural rubber, polyisoprene,styrene-butadiene, or styrene-propylene-diene rubber, or a mixturethereof. Preferably, the resilient polymer component comprises1,4-cis-polybutadiene having a molecular weight average of about 50,000to about 1,000,000. The amount of resilient polymer component of themantle layer is between about 60 to about 99 weight percent of the totalweight of polymer components. The mantle layer preferably has a flexuralmodulus of greater than about 3.5 MPa. Similarly, the golf ball furtherincludes at least one of a filler, a free-radical initiator, or acrosslinking agent.

[0017] The present invention also provides a method for making a golfball having a multi-layer core comprising forming an inner sphere;forming a soft, elastic, intermediate layer around the inner spherewherein the intermediate layer is less than about 0.01-in thick and hasa flexural modulus of less than about 10,000 psi; molding apart from theinner sphere and intermediate layer, and from elastomeric material twosubstantially hemispherical cups having substantially hemisphericalcavities; placing the inner sphere and intermediate layer between thetwo cups within the cavities; joining the cups to form the golf ballcore having an inner sphere, soft intermediate layer, and an outerlayer; and forming a cover over the golf ball core.

[0018] In a first method, the soft, intermediate layer is formed overthe inner sphere by a dipping method. The inner sphere is lowered into abath of latex or other soft material that is of the correct viscosityand percent solids to leave a very thin layer of material, ofsubstantially uniform thickness, encompassing the inner sphere. In asecond method, the soft, intermediate layer may be applied by a sprayingprocess in which the latex is applied through a nozzle, evenly coatingthe surface of the inner sphere.

[0019] Further, the molding of the cups preferably comprises compressionmolding first and second cups from the elastomeric material on oppositesides of a single mold part. The center, which has been coated with softlatex by a dipping or spraying process, is placed between the two cups,which are then joined at an elevated temperature, causing crosslinkingthere between, to form an outer layer of the core. Alternatively, thelatex dip can be disposed on an inner cover layer of a golf ball. Thestep of joining the cups comprises adhesively attaching the cups to eachother. When the cups are joined, the hemispherical cavities togetherform a spherical cavity, now occupied by the center or inner sphere, andthe cups themselves form the outer layer of the core. Thus, the centeris easily positioned concentrically within the finished ball. In anotherembodiment, the joining of the cups is achieved by compression molding.In still another embodiment, molding further comprises molding nonplanarmating surfaces on the cups adjacent the cavities, wherein joining thecups comprises meshing the mating surfaces.

[0020] Finally, a cover is molded around the core. Any process thatresults in accurate and repeatable central placement of the core withinthe cover is acceptable. Generally, covers are applied by compressionmolding, injection molding or casting cover material over the core.

[0021] The present invention further provides a golf ball, comprising asolid center having a first hardness; an intermediate layer formed overthe solid center having a second hardness less than the first; an outerlayer formed over the intermediate layer having a third hardness greaterthan the first hardness; and a cover. Preferably, the first hardness isbetween about 20 and 40 Shore D, the second hardness is less than about20 Shore D, and the third hardness is greater than about 50 Shore D.

[0022] The invention also relates to a multi-layer golf ball including acore having at least one layer; a cover disposed concentrically aboutthe core and having at least one layer; and an intermediate layer formedof a responsive viscoelastic composition disposed between the core andthe at least one cover layer. The responsive viscoelastic compositionincludes at least one material that has a dilatant or thixotropicviscosity, i.e., exhibits an increase in viscosity in response topressure such as shear forces.

[0023] In one embodiment, the intermediate layer is less than about 0.01inches thick. In one preferred embodiment, the intermediate layer isfrom about 0.0005 to 0.01 inches thick. In one more preferredembodiment, the intermediate layer is from about 0.0008 to 0.002 inchesthick.

[0024] In another embodiment, the intermediate layer is from about 0.01to 0.1 inches thick. In one preferred embodiment, the intermediate layeris from about 0.01 to 0.03 inches thick.

[0025] In one embodiment, the intermediate layer is disposed between twocover layers. In another embodiment, the intermediate layer is disposedbetween the core and a second intermediate layer. In yet anotherembodiment, the intermediate layer has a plasticity of about 20 mils to150 mils. In one preferred embodiment, the intermediate layer has aplasticity of about 60 mils to 120 mils.

[0026] In one embodiment, the intermediate layer includes a solid,semi-solid, gel, or gel-like material. In one preferred embodiment, thematerial can include at least one of polydimethyl siloxane, dimethylcyclosiloxane, a hydroxy-terminated polydimethyl siloxane, polyvinylalcohol, an acrylic plastisol, an acrylic organosol, a hydrocarbon-basedgel, a sulfonate ionomer, butyl rubber ionomer, an ionized crosslinkedpolyacrylamide gel, a microporous fast-response gel, a thermoplasticelastomer gel, or a blend thereof. In particular, one suitable blend isa blend of at least one hydrocarbon-based gel with at least onesulfonate ionomer.

[0027] In one embodiment, the intermediate layer material has a hardnessof less than about 90 Shore A. In one preferred embodiment, the materialhas a hardness of less than about 70 Shore A. In one embodiment, thecover has a thickness of about 0.02 to 0.1 inches.

BRIEF DESCRIPTION OF DRAWINGS

[0028] Further features and advantages of the invention can beascertained from the following detailed description provided inconnection with the drawing(s) described below:

[0029]FIG. 1 is a sectional view of the ball of the present invention;

[0030]FIG. 2 is an elevational view of such apparatus;

[0031]FIG. 3 is a plan view of the core-treating apparatus; and

[0032]FIG. 4 is a flow chart of the method of forming an inner sphereaccording to the present invention.

DEFINITIONS

[0033] The term “about,” as used herein, should be understood to referto both numbers in a range of numbers.

[0034] As used herein, the term “fluid” includes a liquid, a paste, agel, a gas, or any combination thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Referring to FIG. 1, ball 10 includes a cover 11 and a core 12.The core 12 has a center or inner sphere 13 that is disposedconcentrically therein and can be comprised of a solid or fluid-filledcenter 14 in a cavity within a soft intermediate layer 15. The core 12may also have an outer mantle 16, which surrounds the inner sphere 13.The solid center of the ball is typically and preferably spherical, maybe solid or fluid-filled, and is generally about 0.5 inches to 1.5inches, preferably about 0.5 inches to 1.35 inches, and more preferablyabout 0.75 to 1.25 inches in diameter. The soft intermediate layer canhave a thickness of about 0.0005 to 0.010 inches, preferably about0.0008 to 0.005 inches. The mantle can have a thickness of about 0.1 to0.6 inches, preferably about 0.15 to 0.35 inches, more preferably about0.2 to 0.3 inches. The entire core, including the center, softintermediate layer, and mantle, can have a diameter of about 1.45 to1.60 inches, preferably about 1.50 to 1.58 inches. The diameters of thesoft intermediate layer and mantle corresponding to a particular center,and of the cover formed around the mantle and center, may be adjustedaccording to the diameter of the center to provide a golf ball formedaccording to the invention with the overall minimum diameter required bythe USGA.

[0036] The central sphere, or center, may be of any dimension orcomposition. It could be a thermoset solid rubber sphere, athermoplastic solid sphere, wood, cork, metal, or any material known toone skilled in the art of ball manufacture. Similarly it could be afluid-filled sphere such as a rubber sack, a thermoplastic, or metallicshell design. A liquid of any composition or viscosity known to those ofordinary skill in the art could be included. It is also feasible toconstruct such a center with a void or “gas” center.

[0037] A representative and preferred base composition for forming thegolf ball center 13, prepared in accordance with the present invention,comprises polybutadiene and, in parts by weight based on 100 partspolybutadiene, 20-50 parts of a metal salt diacrylate, dimethacrylate,or monomethacrylate, preferably zinc diacrylate. The polybutadienepreferably has a cis-1,4-polybutadiene content of above about 90% andmore preferably above about 96%. Commercial sources of polybutadieneinclude “CARIFLEX” BR 1220 manufactured by Shell Chemical, “NEOCIS” BR40manufactured by Enichem Elastomers, and “UBEPOL” BRI 50 manufactured byUbe Industries, Ltd. If desired, the polybutadiene can also be mixedwith other elastomers known in the art, such as natural rubber, styrenebutadiene, and/or isoprene in order to further modify the properties ofthe center 13. When a mixture of elastomers is used, the amounts ofother constituents in the core composition are based on 100 parts byweight of the total elastomer mixture.

[0038] Metal salt diacrylates, dimethacrylates, and monomethacrylatessuitable for use in this invention include those wherein the metal ismagnesium, calcium, zinc, aluminum, sodium, lithium or nickel. Zincdiacrylate is preferred, because it provides golf balls with a highinitial velocity in the USGA test. Suitable, commercially available zincdiacrylates include those from Sartomer. The preferred concentrations ofzinc diacrylate that can be used are about 15 to 30 phr and preferablyabout 18 to 25 phr based upon 100 phr of polybutadiene or alternately,polybutadiene with a mixture of other elastomers that equal 100 phr.

[0039] Free radical initiators are used to promote cross-linking of themetal salt diacrylate, dimethacrylate, or monomethacrylate and thepolybutadiene. Suitable free radical initiators for use in the inventioninclude, but are not limited to peroxide compounds, such as dicumylperoxide, 1,1-di (t-butylperoxy) 3,3,5-trimethyl cyclohexane, a-a bis(t-butylperoxy) diusopropylbenzene, 2,5-dimethyl-2,5 di (t-butylperoxy)hexane, or di-t-butyl peroxide, and mixtures thereof. Other usefulinitiators would be readily apparent to one of ordinary skill in the artwithout any need for experimentation. The initiator(s) at 100% activityare preferably added in an amount ranging between about 0.05 phr and 2.5phr based upon 100 parts of butadiene, or butadiene mixed with one ormore other elastomers. More preferably, the amount of initiator addedranges from about 0.15 phr to 2 phr and most preferably from about 0.25phr to 2.0 phr.

[0040] A typical prior art golf ball core incorporates 5 phr to 50 phrof zinc oxide in a zinc diacrylate-peroxide cure system that cross-linkspolybutadiene during the core molding process. In the present invention,some of the zinc oxide can be eliminated in favor of calcium oxide inthe golf ball core composition. The cores and balls produced from suchan admixture typically exhibit enhanced performance properties. Theinitial velocity of the standard ball is maintained, but the compressionof the ball is reduced by at least about 2 compression points on thestandard compression scale. On the other hand, the combination of theuse of some calcium oxide and a higher percentage of zinc diacrylate canbe used to maintain the same compression, but the initial velocity issignificantly increased. Where the amount of zinc oxide incorporated inprior art cores is typically about 5 phr to 50 phr, the amount ofcalcium oxide added to the core-forming composition of the invention asan activator is typically in the range of about 0.1 to 15, preferablyabout 1 to 10, most preferably about 1.25 to 5, parts calcium oxide perhundred parts of rubber.

[0041] The compositions of the present invention may also includefillers, added to the elastomeric composition to adjust the densityand/or specific gravity of the core. As used herein, the term “fillers”includes any compound or composition that can be used to vary thedensity and other properties of the subject golf ball core. The fillersuseful according to the invention are generally inorganic, and suitablefillers include numerous metals, metal oxides, and inorganic compounds,such as zinc oxide and tin oxide, and barium sulfate, zinc sulfate,calcium carbonate, barium carbonate, clay, tungsten, tungsten oxide,tungsten carbide, an array of silicas, ground particles of cured rubber(which can include recycled core molding matrix ground to about 20 to 40mesh particle size), coloring agents, and the like. The fillers, whenused, may be present in an amount of about 0.5 to 50 weight percent ofthe composition. The amount and type of filler utilized is partlygoverned by the amount and weight of other ingredients in thecomposition, since a maximum golf ball weight of 1.620 oz (45.92 g) hasbeen established by the USGA. Appropriate fillers generally used rangein specific gravity from about 2 to 20. In the preferred embodiment, thecenter contains an amount of filler such that the specific gravity ofthe center is greater than the specific gravity of the mantle layer.

[0042] In the golf ball center 13, as shown in FIG. 1, the preferredrange of specific gravities in one embodiment can be from about 1.1 toabout 1.7, more preferably in the range of about 1.1 to about 1.4,depending upon the size of the center, soft intermediate layer, cover,mantle layer and finished ball, as well as the specific gravity of thecover and mantle layer.

[0043] Antioxidants may also be included in the elastomer centersproduced according to the present invention. Antioxidants are compoundswhich prevent the breakdown of the elastomer. Antioxidants useful in thepresent invention include, but are not limited to, quinoline typeantioxidants, amine type antioxidants, and phenolic type antioxidants.

[0044] Other ingredients such as processing aids, processing oils,plasticizers, dyes and pigments, as well as other additives well knownto the ordinary-skilled artisan may also be used in the presentinvention in amounts sufficient to achieve the purpose for which theyare typically used.

[0045] A center 13 can also be a fluid-filled sphere, filled with a widevariety of materials including air, water solutions, gels, foams,hot-melts, other fluid materials and combinations thereof, as set forthin U.S. Pat. No. 5,683,312 the disclosure of which is incorporatedherein by reference thereto.

[0046] The half-shells, and resultant mantle, for use in a ball coreinclude a resilient polymer component, which is used as the majority ofpolymer in the composition and method. Resilient polymers suitable foruse in the ball core include polybutadiene, polyisoprene,styrene-butadiene, styrene-propylene-diene rubber (EPDM), and mixturesthereof. The resilient polymer component is preferably polybutadiene andmore preferably 1,4-cis-polybutadiene. One example of a1,4-cis-polybutadiene is “CARIFLEX” BR 1220, commercially available fromShell. The polybutadiene or other resilient polymer component may beproduced with any suitable catalyst that results in a predominantly1,4-cis content, and preferably with a catalyst that provides a high1,4-cis content and a high molecular weight average, defined as being atleast about 50,000 to 1,000,000, preferably from about 250,000 to750,000, and more preferably from about 200,000 to 325,000. The 1,4-ciscomponent of polybutadiene is generally the predominant portion of theresilient polymer component when polybutadiene is present. “Predominant”or “predominantly” is used herein to mean greater than 50 weightpercent. The 1,4-cis component is preferably greater than about 90weight percent, and more preferably greater than about 95 weightpercent, of the polybutadiene component. The resilient polymer componentis typically present in an amount of at least about 60 weight percent,preferably about 65 to 99 weight percent, and more preferably about 75to 90 weight percent of the polymer blend. The term “polymer blend” isused herein to mean the blend of the resilient polymer component and areinforcing polymer component.

[0047] The mantle may also include a reinforcing polymer component whichshould have a viscosity sufficiently low enough, at the mixingtemperature, to permit proper mixing of the two polymer components. Thereinforcing polymer component typically has a glass transitiontemperature, T_(g), (and if crystalline, a crystalline melting point)sufficiently low to permit mixing with the resilient polymer componentwhile avoiding substantial crosslinking or thermal degradation of theresilient component at the mixing temperature. Examples of polymerssuitable for use as the reinforcing polymer component include:transpolyisoprene, block copolymer ether/ester, acrylic polyol, apolyethylene, a polyethylene copolymer, 1,2-polybutadiene(syndiotactic), ethylene-vinyl acetate copolymer, cyclooctene,trans-polybutadiene, and mixtures thereof. Particularly suitablereinforcing polymers include: a transpolybutadiene, such as “FUREN” 88obtained from Asahi Chemicals of Yako, Kawasakiku, Kawasakishi, Japan;“KURARAY” TP251, a transpolyisoprene commercially available from KurarayCo. of New York, N.Y. as Kuraray America Co.; “LEVAPREN” 700HV, anethylene-vinyl acetate copolymer commercially available fromBayer-Rubber Division, Akron, Ohio; and “VESTENAMER” 8012, a cyclooctenecommercially available from Hüls America Inc. of Tallmadge, Ohio. Somesuitable reinforcing polymer components are listed below with theircrystalline melting points and/or T_(g). Crystalline Melt TemperaturePolymer Type Tradename (° C.) T_(g) (° C.) Transpolyisoprene KURARAYTP251 60 −59 Transpolybutadiene FUREN 88 84 −88 Polyethylene Dow LDPE 98−25 Polyoctene VESTENAMER 8012 54 −65

[0048] The reinforcing polymer component is preferably present in anamount sufficient to impart rigidity to the shells during processing,yet not undesirably reduce resilience of the crosslinked polymer blendand thereby have an undesirable effect on the final product. Theviscosity of materials suitable for use in the invention may be readilydetermined by one of ordinary skill in the art. The viscosity cangenerally be below about 1,000,000 poise to readily permit mixing. Whentranspolyisoprene is used as the reinforcing polymer component, it istypically present in an amount of about 10 to 40 weight percent,preferably about 15 to 30 weight percent, of the polymer blend. Theweight of the reinforcing polymer relative to the total compositiongenerally ranges from about 5 to 25 weight percent, preferably about 10to 15 weight percent. The uncrosslinked mantle should have a flexuralmodulus, as measured under ASTM D790M-93, Method II, of greater thanabout 3.5 MPa, and preferably greater than about 7 MPa. The reinforcingpolymer components imparts a degree of rigidity to the shells sufficientto maintain the desired shape until the first mixture is crosslinked.

[0049] Suitable crosslinking agents include one or more metallic saltsof unsaturated fatty acids or monocarboxylic acids, such as zinc,calcium, or magnesium acrylate salts, and the like. Preferred acrylatesinclude zinc acrylate, zinc diacrylate, and zinc methacrylate. Thecrosslinking agent is preferably present in an amount sufficient tocrosslink the various chains of polymers in the polymer blend tothemselves and to each other. The desired elastic modulus for the mantlemay be obtained by adjusting the amount of crosslinking by selecting aparticular type or amount of crosslinking agent. This may be achieved,for example, by altering the type and amount of crosslinking agent,which method is well known to those of ordinary skill in the art. Thecrosslinking agent is typically added in an amount from about 1 phr to50 phr of the polymer blend, preferably about 20 phr to 45 phr, and morepreferably about 30 phr to 45 phr, of the polymer blend.

[0050] Although not required, a free-radical initiator is preferablyincluded in the composition and method. The free-radical initiator maybe any compound or combination of compounds present in an amountsufficient to initiate a crosslinking reaction between a crosslinkingagent and the reinforcing and resilient polymer components of thepolymer blend. The free-radical initiator is preferably a peroxide.Suitable free-radical initiators includedi(2-t-butyl-peroxyisopropyl)benzene peroxide,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide,di-t-butyl peroxide, 2,5-di-(t-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(t-butylperoxy)valerate on calcium silicate, lauroylperoxide, benzoyl peroxide, t-butyl hydroperoxide, and the like. Thefree-radical initiator is preferably present in an amount of up to 2phr, more preferably about 0.2 to 1 phr of the polymer blend.

[0051] The resilient polymer component, reinforcing polymer component,free-radical initiator, and any other materials used in forming the golfball center and core, in accordance with invention, may be combined byany type of mixing known to one of ordinary skill in the art. Theoptional crosslinking agent, and any other optional additives used tomodify the characteristics of the golf ball center, may similarly becombined by any type of mixing. Suitable mixing equipment is well knownto those of ordinary skill in the art, such as a Banbury mixer.Conventional mixing speeds for combining polymers are typically used,although the speed is preferably high enough to impart substantiallyuniform dispersion of the resilient and reinforcing polymer components.On the other hand, the speed should not be too high, as high mixingspeeds tend to break down the polymers being mixed and particularly mayundesirably decrease the molecular weight of the resilient polymercomponent. The speed should thus be low enough to avoid high shear,which may result in loss of desirably high molecular weight portions ofthe resilient polymer component. Also, too high a mixing speed mayundesirably result in creation of enough heat to initiate thecrosslinking before the preforms are shaped and assembled around a core.The mixing temperature depends upon the type of resilient andreinforcing polymer components, and more importantly, on the type offree-radical initiator. The mixing temperature is preferably higher thanthe melting temperature of the reinforcing polymer, but not so high asto initiate substantial crosslinking. For example, when usingdi(2-t-butyl-peroxyisopropyl)benzene peroxide as the free-radicalinitiator, a mixing temperature of about 80°C. to 125°C., preferablyabout 88°C. to 110°C., and more preferably about 90°C. to 100°C. issuitable to safely mix the ingredients. The mixing speed and temperatureare readily determinable by one of ordinary skill in the art withoutundue experimentation.

[0052] The mantle layer may alternatively comprise a thermoplasticcopolyesterester block copolymer, dynamically vulcanized thermoplasticelastomer, styrene-butadiene elastomer with functional groups such asmaleic anhydride or sulfonic acid attached, thermoplastic polyurethaneor polymers made using a metallocene catalyst, or blends thereof.Suitable thermoplastic copolyetheresters include “HYTREL” 3078 and“HYTREL” G4078W which are commercially available from DuPont ofWilmington, Del. Suitable dynamically vulcanized thermoplasticelastomers include “SANTOPRENE”, and “SARLINK”, commercially availablefrom Advanced Elastomer Systems. Examples of suitable functionalizedstyrene-butadiene elastomers, include “KRATON” FG-1901x and FG-1921x,which are available from the Shell Corporation. Examples of suitablethermoplastic polyurethanes include “ESTANE” 58133 and “ESTANE” 58144,which are commercially available from the B.F. Goodrich Company.Further, the materials for the mantle layer described above may be inthe form of a foamed polymeric material. For example, suitablemetallocene polymers include foams of thermoplastic elastomers based onmetallocene single-site catalyst-based foams.

[0053] Additionally, the mantle layer may be a blend of a first and asecond thermoplastic, wherein the first thermoplastic is a thermoplasticcopolyetherester or copolyesterester block copolymer, a dynamicallyvulcanized thermoplastic elastomer, a functionalized styrene-butadieneelastomer, a thermoplastic polyurethane or a metallocene polymer and thesecond thermoplastic is a material such as a thermoplastic polyurethane,a thermoplastic polyetherester or polyetheramide, a thermoplasticionomer resin, a thermoplastic polyester, another dynamically vulcanizedelastomer, another functionalized styrene-butadiene elastomer, anothermetallocene polymer or blends thereof.

[0054] Suitable thermoplastic polyetheramides include “PEBAX” 2533,“PEBAX” 1205 and “PEBAX” 4033 which are available from Elf-Atochem ofPhiladelphia, Pa. Suitable thermoplastic ionomer resins include anynumber of olefinic based ionomers including “SURLYN” and “IOTEK”, whichare commercially available from DuPont and Exxon, respectively. Suitablethermoplastic polyesters include polybutylene terephthalate. Likewise,the dynamically vulcanized thermoplastic elastomers, functionalizedstyrene-butadiene elastomers, thermoplastic polyurethane or metallocenepolymers identified above are also useful as the second thermoplastic insuch blends. Further, the materials of the second thermoplasticdescribed above may be in the form of a foamed polymeric material.

[0055] In addition to their use in golf ball centers, fillers can alsobe added to the mantle layer composition or both ball portions toincrease the density of the core to conform to uniform golf ballstandards. Fillers may also be used to modify the weight of the core forspecialty balls used by players, e.g., a lower weight core is preferredfor a player having a low swing speed. Fillers typically includeprocessing aids or compounds to affect rheological and mixingproperties, the specific gravity, the modulus, the tear strength,reinforcement, and the like. The fillers are generally inorganic, andsuitable fillers include numerous metals and metal oxides, such as zincoxide and tin oxide, and barium sulfate, calcium carbonate, bariumcarbonate, clay, tungsten, tungsten carbide, tungsten oxide, silicas,and the like. The fillers, when used, may be present in an amount ofabout 0.5 to 50 weight percent of the composition.

[0056] Turning to FIGS. 2 and 3, the dipping apparatus 17 includes a diptank 18 filled to level 18 a and agitated by electric mixer 18 m.Apparatus 17 also includes oval conveying rack 19 with ball corecarriers 20. Dip tank 18 is filled with latex bath 18 b to level 18 aand, if latex has been in tank 18 for a substantial length of time,initial mixing of bath 18 b in tank 18 can be carried out untiluniformity of bath 18 b is reached. After such mixing golf ball cores 21are loaded at loading station 22 into holding carriers 20 eachcomprising a stem 20 a and a holder ring 20 b. Loaded carriers 20 arecarried by conveying rack 19 along and down to dip centers 21 for 1 to60 seconds into latex bath 18 b. Rack 19 moves through a descendingportion 23, dipping portion 24 and ascending portion 25 of the carriercircuit to accomplish the latex dip core treatment. In solid cores thelatex forms an encapsulating coating on the core of about 0.0005 inchesto about 0.01 inches thick.

[0057] After the ball centers 21, for example, exit dip tank 18, theypass into a curing chamber 26 in which heat, ultraviolet rays, or othermeans for accelerating cure may be applied. It will be understood thatsome latex bath materials cure sufficiently under ambient conditionsthat curing chamber 26 is not required.

[0058] Depending on the nature of the latex material applied, the golfball dip-treated portions can then be stored for a period of time foradditional cure, or, if the latex material is sufficiently cured at thispoint, the latex dip-encapsulate ball portion can be transporteddirectly to the molding area for molding of the outer cover layer orother cover material.

[0059] Since some latex materials generate fumes in the dip tank 18, itis preferred to have a vacuum hood 27 positioned above the dip tank 18.The vacuum hood 27 is preferably provided with means (not shown) forgenerating a clean air curtain about the periphery of the dip tank 18 toprevent escape of undesirable gasses. The curing chamber 26 can also beprovided with suitable gas removal means.

[0060] The thermosetting latex materials that are useful in the one ormore intermediate layers of the present invention are any materials thatwill withstand the temperatures at which the mantle materials aremolded, particularly in situations where the mantle is molded directlyadjacent the thermosetting latex material(s). It should be understoodthat these latex or other soft materials may be used in a core layer,intermediate layer, or a cover layer, but preferably they are includedin an intermediate layer or used to form at least one intermediatelayer. Typical thermosetting latex materials that can be used to coatthe cores include low ammonia natural latex and/or pre-vulcanizednatural latex. Natural latex is noted for its combination of hightensile strength, excellent elasticity, tack, low modulus, and abilityto form strong, coherent, wet and dry films. These characteristics makeit ideal for manufacturing dipped articles and no other polymersubstitute has been found which possesses all of these properties.

[0061] Preferred latex materials, such as “HARTEX” 101 or “HARTEX” 103from Firestone, of Akron, Ohio, or “HEVEATEX” H1704 pre-vulcanizednatural latex, are partially pre-vulcanized natural latexes that can bediluted with water to any solid content. It is understood that non-latexencapsulating materials may also be used. Such materials includeelastomer adhesives as well as aqueous and non-aqueous adhesives, andare represented by the following, but noninclusive examples. Elastomeradhesives, such as a “CHEMLOK” 252H, are sold by the Lord Corporation;urethane dispersions, such as “AQUATHANE”, are sold by ReichholdChemicals, Inc.; aqueous adhesives, such as “CHEMLOK” EP6962-62, aresold by the Lord Corporation; non-aqueous adhesives, such as “SILAPRENE”DC-11687, are sold by the Uniroyal Technology Corporation; syntheticlatexes, such as carboxylated “NBR” latex and “THIXON”, are sold byReichhold Chemicals, Inc., Morton International; and GuardsmanChemicals, Inc., respectively. Alkyd resins, such as “VPI” alkyd resin,are sold by the Ball Chemical Company.

[0062] Other materials that could be suitable for the soft, intermediatelayer, include aqueous acrylic and latex copolymers, such as “RHOPLEX”2438 emulsion, “RHOPLEX” E-32 NP emulsion, and many commercial products,many of which have properties that suggest use as the soft intermediatelayer developed herein.

[0063] The soft intermediate layer may also contain additives, fillers,thickeners, or a combination thereof, to adjust the specific gravity ofthe layer to alter various golf ball properties as needed or desired.“RENACIT” 7 is a peptizer produced by Miles, Inc of Pittsburgh, Pa.,that is a pentachlorothiophenol mixture containing Kaolin, quartz, andmineral oil. Materials such as “RENACIT” 7 can be used to alter theproperties of the inner surface of the mantle layer. Specifically, itcan be used to soften the inner surface. Fillers may also be added tothe intermediate layer. Fillers typically include processing aids orcompounds to affect theological and mixing properties, the specificgravity, the modulus, the tear strength, reinforcement, and the like.Suitable fillers include the same fillers described herein for use inthe core or center. Preferably, fillers, when used in the intermediatelayer, may be present in an amount of about 0.5 to 50 weight percent ofthe composition. In one preferred embodiment, the filler is present inan amount of about 0.5 to 20 weight percent. In one preferredembodiment, the fillers include zinc oxide.

[0064] Film thickness is an important parameter to consider in theformation of the soft, elastomeric, intermediate layer. Film thicknessof a natural or synthetic latex material can be controlled by adjustingparameters such as the time that the ball center remains in the latexbath or percent solids of the latex. Most commonly, controlling filmthickness is accomplished by adjusting the weight percent of the totalsolids. For example, a low ammonia natural latex compound, such as“HARTEX” 101 or “HARTEX” 103 from Firestone, of Akron, Ohio, containing30% solids using a 30-second dwell time produces a film thickness of0.007 inches.

[0065] The intermediate layer can also include, or be formed entirelyfrom, a responsive viscoelastic composition. These compositions includesolids, semi-solids, gels, or gel-like materials that have a rheopectic,dilatant, or thixotropic viscosity that exhibit an increase in viscosityin response to shear forces, tensile forces, compressive strain, or acombination thereof. Indeed, the material can be formed as a coating orfilm disposed about a portion of a golf ball, preferably entirelysurrounding the portion of the ball being coated; or the material can beformed by any conventional golf ball layer forming method includingcompression, injection, or reaction injection molding, casting, or thelike, depending upon the material. Preferably, the responsiveviscoelastic composition forms at least one continuous layer ofmaterial. In this embodiment, the intermediate layer can be placed atany point in the ball between the inner layer of the core and the outercover layer. In one preferred embodiment, the intermediate layerincluding responsive viscoelastic material is disposed between themantle and the outer cover layer, while in another it is disposeddirectly adjacent the core.

[0066] Without being bound by theory, it is believed that the materialprovides for low resistance to low shear stresses from low clubheadspeeds, but higher resistance to high shear stresses from a higherclubhead speeds. Immediate responses are dilatant, while delayedresponses that are time dependent are considered rheopectic. Preferably,the response is dilatant, or immediately upon application of the shearstress. The response of the responsive viscoelastic material isreversible. As a result, it is believed that a golf ball having a higheffective modulus and a relatively hard compression would effectivelyhave a softer compression, more distortion from a lower effectivemodulus, and a softer feel when struck at a low clubhead speed. Such agolf ball according to the invention advantageously has the propertiesdesired by both beginning and more advanced players, since the ball'sproperties will be varied depending upon the swing speed of the golfclub when it strikes the ball of the invention.

[0067] Suitable responsive viscoelastic compositions includepolysiloxane compositions, such as dilatant silicone composition 3179available from Dow Corning and described in U.S. Pat. No. 2,541,851, thedisclosure of which is incorporated herein by reference thereto. Suchmaterials have high elasticity, a high COR. Preferred polysiloxanecompounds typically have a plasticity of about 20 mils to 150 mils,preferably of about 60 mils to 120 mils, and more preferably of about 65mils to 100 mils, as measured by ASTM D-926. Preferred polysiloxanecompounds also preferably have a specific gravity of 1.1 to 1.18 g/cm³.In one embodiment, the tensile strength of the silicones is from about10 psi to 250 psi, while in another embodiment, the tensile strength isfrom about 800 psi to 100,000 psi. In one preferred embodiment, thetensile strength of the silicone material is from about 1000 psi to10,000 psi. Preferred polysiloxane compositions include polydimethylsiloxane, dimethyl cyclosiloxane, a hydoxy-terminated polydimethylsiloxane polymers. These polysiloxane compositions can also include oneor more inert additives, such as TiO₂, silica, quartz, boric acid,glycerine, and the like.

[0068] Additional suitable responsive viscoelastic compositions includeessentially uncured polybutadiene, or lightly cured polybutadiene havinga low level of peroxide, zinc oxide and less than about 10 phr of zincdiacrylate or another α,β-unsaturated carboxylic acid or derivativethereof. “Low level” of peroxide typically refers to less than about 5percent, preferably less than about 1 percent, more preferably less thanabout 0.1 percent, and most preferably less than about 0.05 percent ofperoxide. The uncured polybutadiene may optionally be blended with up toabout 50 percent by weight of trans-polyisoprene (synthetic), balata(natural trans-polyisoprene), polyoctenamer, or any of the otherrigidifying polymers described herein, or a combination thereof, tofacilitate molding or other desirable processing or final productcharacteristics. In one embodiment, the rigidifying polymer is presentin an amount of about 10 to 40 weight percent, while in anotherembodiment it is present in an amount of about 20 to 30 weight percent.

[0069] Other suitable responsive viscoelastic compositions for useaccording to the invention include: (a) the oil containing resinsdescribed in U.S. Pat. No. 4,829,093, as well as combinations of one ormore oil-containing copolymers and one or more thermoplastic resins; (b)modeling dough compositions described in U.S. Pat. Nos. 5,498,645;5,171,766; 5,506,280; 5,364,892; 5,972,092, with or without hollowmicrospheres; (c) copolymer dispersions having a narrow particledispersion as described in U.S. Pat. Nos. 4,371,636; 4,654,396; and5,037,880, which contain unsaturated carboxylic acids (acrylic acid,methacrylic acid, and the like), a monoolefinically unsaturated monomer(vinyl esters such as styrene, esters of acrylic acids with alkanols,and the like), and additives (emulsifiers, dispersants, and the like);(d) dilatant compositions including a plurality of particulates, one ormore non-volatile emollients, and gelling agent(s), as described in U.S.Pat. No. 5,883,382; (e) synthetic resin dispersions stabilized byprotective colloids, such as those described in U.S. Pat. No. 5,679,735;(f) Organosol gels of controlled rigidity, which typically include ahigh MW thermoplastic core, as described in U.S. Pat. No. 5,698,616; (g)a solution of a sulfonated polystyrene ionomer or sulfonated EPDM orbutyl rubber ionomer, such as disclosed in U.S. disclosure H363; (h)sodium tetraborate crosslinked polyvinylacetate compositions; (i)gellants based on oil-based well bore fluids, as disclosed in U.S. Pat.No. 5,021,170; (j) a hydrocarbon-based gel, a sulfonate ionomer, orblends thereof, such as disclosed in U.S. Pat. No. 4,536,310; (k)acrylic plastisols or organosols, such as disclosed in U.S. Pat. No.4,465,572, such as photosensitive thermally coalescible acrylicplastisols or organosols; (l) responsive gels that meet the responsiveviscoelastic composition disclosed herein, as disclosed in U.S. Pat. No.5,827,459; and the like, including polyvinyl alcohol, an ionizedcrosslinked a polyacrylamide gel, a microporous fast-response gel, athermoplastic elastomer gel, or a blend thereof. The disclosure of eachof the above patents is incorporated herein by express referencethereto. Further, one of ordinary skill in the art aware of suchmaterials will be readily able to include them in golf balls preparedaccording to the invention. Combinations of any suitable responsiveviscoelastic compositions with each other or conventional materials arealso contemplated.

[0070] When non-responsive viscoelastic materials are included in thecomposition, they are typically present in an amount of less than about50 weight percent of the composition. In various embodiments, suchnon-responsive viscoelastic materials are present in amounts less thanabout 20 weight percent, less than about 10 weight percent, less thanabout 5 weight percent, less than about 1 weight percent, and less thanabout 0.1 weight percent.

[0071] While some of the responsive viscoelastic compositions describedherein are difficult to process, i.e., are very viscous liquids or gels,or tacky solids, they may be encased in a thin film of a material thatrenders the composition(s) more suitable for processing. For example,the materials can be cast onto the inner surface of half shells of anouter cover material for subsequent compression molding.

[0072] Any of the responsive viscoelastic compositions can be modifiedwith various conventional additives, so long as the additive(s) do notsubstantially reduce the responsive properties of the material. Forexample, a density-modifying filler, fiber, flake, particulate,thermoplastic, or glass microballoon may be included, as well as any ofthe other suitable fillers described herein with respect to other layersof the golf ball. Various fillers described in U.S. Pat. Nos. 6,127,457;5,895,805; 5,607,993; and 5,202,362 can be included individually or inany combination, and these patent disclosures are incorporated herein byexpress reference thereto.

[0073] In one embodiment, FIG. 1 depicts a golf ball having an innercore 14, an outer core 15, an intermediate layer 16 formed of aresponsive viscoelastic composition, and a cover 11. Although it shouldbe understood that the invention encompasses covers having multiplelayers, this embodiment depicts a cover 11 having a single layer. Also,the inner and outer core layers 14, 15 could be produced as a singleunitary core (not depicted).

[0074] In another embodiment, FIG. 1 depicts golf ball 10 formed of aunitary core 14, an intermediate layer 15 formed of a responsiveviscoelastic composition, an inner cover layer 16, and an outer coverlayer 11. In yet another embodiment, FIG. 1 depicts a golf ball 10formed of a core 14, an inner cover layer 15, an intermediate layer 16formed of a responsive viscoelastic composition, and an outer coverlayer 11. In each of the above shown embodiments of FIG. 1, it should beunderstood that the thicknesses are not necessarily drawn to scale.Also, with respect to each embodiment of the invention, the core caninclude one or more layers and be a solid, wound, fluid-filled, or anyother type of construction available to one of ordinary skill in theart. In yet another embodiment (not shown), the golf ball of theinvention includes a core, a first intermediate layer formed of aresponsive viscoelastic composition, an inner cover layer, a secondintermediate layer formed of a responsive viscoelastic composition, anda cover, each disposed in concentric fashion about the previous layer.

[0075] A first preferred embodiment includes a thin, stiff outer covermaterial of ionomer, high acid ionomer, polyamide, polyurethane,polyurethane ionomer, or the like having a shore D hardness of greaterthan about 60 and a thickness of about 0.001 inches to 0.03 inches, withan intermediate layer including the responsive viscoelastic compositiondisposed directly adjacent and inwardly of the outer cover layer anddirectly adjacent the core. The intermediate layer of this embodimentcan have a thickness of about 0.03 inches to 0.1 inches. Also, theintermediate layer typically has a Shore D hardness of less than about50, preferably a hardness of less than about 90 Shore A, and morepreferably less than about 70 Shore A.

[0076] A second preferred embodiment is the same, but further includesan inner cover layer of the same materials, or even the same materials,between the core and the intermediate layer. In one embodiment, theouter cover layer includes a polyurethane, preferably a castpolyurethane material and the inner cover layer includes at least oneionomer. A third preferred embodiment is similar to the first, but theintermediate layer is disposed inwardly from both an inner and an outercover layer. In various embodiment of this third preferred embodiment,the hardness of the inner and outer cover layers can be adjusted so thatone layer is harder than the other.

[0077] Referring now to FIG. 4, the most preferred molding process usesa mold assembly 30 comprising a upper or top mold frame 31, a lower orbottom mold frame 32 and a center mold frame 33. The top and bottom moldframes 31 and 32 include a plurality of mating cavities 34 and 35 thatform a sphere the size of a golf ball core as set forth above. Thecenter mold frame 33 includes a plurality of protrusions 36 on oppositesides of the center mold frame for corresponding with the cavities 34and 35 of the top and bottom mold frames. The protrusions 36 arehemispheres that are substantially the same size as one half of the ballcenter as set forth above.

[0078] First, as shown in Step 1, the mantle material such aspolybutadiene preps 37 are placed in the cavities 34 and 35 of the topand bottom mold frames. Then referring to Step 2A, the center mold frame33 is moved into alignment with the bottom mold frame 32 such that theprotrusions 36 are located in alignment or coaxial with the cavities 35.However, the center mold frame 33 is positioned over the bottom moldframe 32 at such a height that the polybutadiene preps are onlycompressed enough to hold them in place. Then, as shown in Step 2B and2C, the center mold frame 33 and the bottom mold frame 32 are moved intoalignment with the top mold frame 31 such that the protrusions 36 andthe cavities 34 and 35 are all in alignment. Again, the center moldframe 33 is spaced from the top mold frame 31 such that the preps in thetop mold frame cavities 34 are only slightly compressed.

[0079] Once the mold assembly 30 is in position, the mold assembly 30 isplaced into a press, heated and compressed, as shown in Step 3.Preferably, the mold assembly 30 is heated to a first temperature thatmakes the polybutadiene preps significantly more pliable, but is belowthe cure initiation points. Preferably, the temperature is greater thanabout 150° F., but less that the cure initiation point. The mostpreferred temperature is between about 190° F. and 220° F. The moldassembly 30 is compressed to a pressure sufficient enough to formhemispheres from the polybutadiene preps, as shown in Step 4.Preferably, the mold assembly is compressed to a pressure of about 700psi to 1400 psi and, more preferably, it is compressed to a pressure ofabout 1000 psi. The mold is then cooled to about 60° F. to 100°F. andpreferably, it is cooled to about 80° F.

[0080] After the mantle material, e.g., the polybutadiene preps, havebeen formed into hemispheres, the mold assembly is removed from thepress and the top mold frame 31, bottom mold frame 32 and the centermold frame 33 are moved out of alignment, as shown in Step 4. Then,turning to Step 5, the ball centers 13 with intermediate layer 15 (SeeFIG. 1) are placed within the hemispheres located in the bottom moldframe 32. The top mold frame 31 is moved into alignment with the bottommold frame such that the mantle hemispheres form a sphere around theball centers 13. Then the top and bottom mold frames 31 and 32 areplaced back into the press, heated and compressed again. This time, thetop and bottom mold frames are heated to a temperature above the cureinitiation for the polybutadiene forming the mantle preps. Preferably,the mold frames are heated to a temperature of greater than about 290°F. and are compressed a pressure of greater than about 2000 psi.

[0081] Referring to FIG. 1, the cover 11 provides the interface betweenthe ball 10 and a club. Properties that are desirable for the cover aregood moldability, high abrasion resistance, high tear strength, highresilience, and good mold release, among others.

[0082] The cover 11 can be comprised of polymeric materials such asionic copolymers of ethylene and an unsaturated monocarboxylic acidwhich are available under the trademark “SURLYN” of E.I. DuPont deNemours & Company of Wilmington, Del. or “IOTEK” or “ESCOR” from Exxon.These are copolymers or terpolymers of ethylene and methacrylic acid oracrylic acid partially neutralized with zinc, sodium, lithium,magnesium, potassium, calcium, manganese, nickel or the like.

[0083] In accordance with the preferred balls, the cover 11 has athickness to generally provide sufficient strength, good performancecharacteristics and durability. Preferably, the cover 11 is of athickness from about 0.03 inches to about 0.12 inches. More preferably,the cover 11 is about 0.04 to 0.09 inches in thickness and, mostpreferably, is about 0.05 to 0.085 inches in thickness.

[0084] In one preferred embodiment, the cover 11 can be formed frommixtures or blends of zinc, lithium and/or sodium ionic copolymers orterpolymers.

[0085] The “SURLYN” resins for use in the cover 11 are ionic copolymersor terpolymers in which sodium, lithium or zinc salts are the reactionproduct of an olefin having from 2 to 8 carbon atoms and an unsaturatedmonocarboxylic acid having 3 to 8 carbon atoms. The carboxylic acidgroups of the copolymer may be totally or partially neutralized andmight include methacrylic, crotonic, maleic, fumaric or itaconic acid.

[0086] The covers of this invention may comprise homopolymeric andcopolymer materials such as:

[0087] (1) Vinyl resins such as those formed by the polymerization ofvinyl chloride, or by the copolymerization of vinyl chloride with vinylacetate, acrylic esters or vinylidene chloride.

[0088] (2) Polyolefins such as polyethylene, polypropylene, polybutyleneand copolymers such as ethylene methylacrylate, ethylene ethylacrylate,ethylene vinyl acetate, ethylene methacrylic or ethylene acrylic acid orpropylene acrylic acid and copolymers and homopolymers produced usingsingle-site catalyst.

[0089] (3) Polyurethanes such as those prepared from polyols anddiisocyanates or polyisocyanates and those disclosed in U.S. Pat. No.5,334,673.

[0090] (4) Polyureas such as those disclosed in U.S. Pat. No. 5,484,870.

[0091] (5) Polyamides such as poly(hexamethylene adipamide) and othersprepared from diamines and dibasic acids, as well as those from aminoacids such as poly(caprolactam), and blends of polyamides with Surlyn,polyethylene, ethylene copolymers, ethyl-propylene-non-conjugated dieneterpolymer, etc.

[0092] (6) Acrylic resins and blends of these resins with poly vinylchloride, elastomers, etc.

[0093] (7) Thermoplastics such as the urethanes, olefinic thermoplasticrubbers such as blends of polyolefins withethylene-propylene-non-conjugated diene terpolymer, block copolymers ofstyrene and butadiene, isoprene or ethylene-butylene rubber, orcopoly(ether-amide), such as “PEBAX” sold by Elf-Atochem ofPhiladelphia, Pa.

[0094] (7) Polyphenylene oxide resins, or blends of polyphenylene oxidewith high impact polystyrene as sold under the trademark “NORYL” byGeneral Electric Company, Pittsfield, Mass.

[0095] (8) Thermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers sold under the trademarks “HYTREL” by E.I. DuPont deNemours & Company of Wilmington, Del. and “LOMOD” by General ElectricCompany, Pittsfield, Mass.

[0096] (9) Blends and alloys, including polycarbonate with acrylonitrilebutadiene styrene, polybutylene terephthalate, polyethyleneterephthalate, styrene maleic anhydride, polyethylene, elastomers, etc.and polyvinyl chloride with acrylonitrile butadiene styrene or ethylenevinyl acetate or other elastomers.

[0097] Blends of thermoplastic rubbers with polyethylene, propylene,polyacetal, nylon, polyesters, cellulose esters, etc.

[0098] Preferably, the cover 11 is comprised of polymers such asethylene, propylene, butene-1 or hexane-1 based homopolymers andcopolymers including functional monomers such as acrylic and methacrylicacid and fully or partially neutralized ionomer resins and their blends,methyl acrylate, methyl methacrylate homopolymers and copolymers,imidized, amino group containing polymers, polycarbonate, reinforcedpolyamides, polyphenylene oxide, high impact polystyrene, polyetherketone, polysulfone, poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethelyne vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers and blends thereof. Still further, the cover 11 is preferablycomprised of a polyether or polyester thermoplastic urethane, athermoset polyurethane, an ionomer such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present in 0 to50 weight percent and Y is acrylic or methacrylic acid present in 5 to35 weight percent. More preferably, in a low spin rate embodimentdesigned for maximum distance, the acrylic or methacrylic acid ispresent in 15 to 35 weight percent, making the monomer a high modulusionomer. In a high spin embodiment, the cover includes an ionomer wherean acid is present in 10 to 15 weight percent and includes a softeningcomonomer.

[0099] Although preferred embodiments of the invention have beenillustrated in the accompanying drawings and described in the foregoingDetailed Description, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements and modifications of parts and elements without departingfrom the spirit of the invention.

What is claimed is:
 1. A multi-layer golf ball comprising: a corecomprising: a center; a intermediate layer formed around the center, theintermediate layer being less than about 0.01 inches thick and having aflexural modulus of less than about 10,000 psi; a mantle comprising atleast one layer, the layer comprising a resilient polymer component,wherein the mantle is disposed concentrically adjacent the intermediatelayer; and at least one cover layer disposed concentrically around themantle; wherein the intermediate layer comprises low ammonia naturallatex and/or pre-vulcanized natural latex, elastomer adhesives, urethanedispersions, aqueous and non-aqueous adhesives, synthetic latexes, alkydresins, acrylic and latex copolymers, polyurethane coatings, or mixturesthereof.
 2. The ball of claim 1 , wherein the intermediate layerthickness is about 0.0005 inches to 0.01 inches.
 3. The ball of claim 2, wherein the intermediate layer thickness is about 0.0008 inches to0.002 inches.
 4. The ball of claim 1 , wherein the intermediate layerhas a Shore A hardness less than about
 90. 5. The ball of claim 4 ,wherein the intermediate layer has a Shore A hardness less than about70.
 6. The ball of claim 1 , wherein the intermediate layer has aflexural modulus less than about 3,000 psi.
 7. The ball of claim 1 ,wherein the center has an outer diameter of about 0.5 inches to 1.35inches.
 8. The ball of claim 7 , wherein the center has an outerdiameter of about 0.75 inches to 1.25 inches.
 9. The ball of claim 1 ,wherein a combination of the center, the soft elastic intermediatelayer, and the mantle has an outer diameter of about 1.45 inches to 1.6inches.
 10. The ball of claim 9 , wherein a combination of the center,the soft elastic intermediate layer, and the mantle has an outerdiameter of about 1.5 inches to 1.58 inches.
 11. The ball of claim 1 ,wherein the center is solid, or filled with a liquid, a gel, a foam, ora gas.
 12. The ball of claim 1 , wherein the mantle layer comprises areinforcing polymer component.
 13. The ball of claim 1 , wherein theresilient polymer component of the mantle layer comprises polybutadiene,natural rubber, polyisoprene, styrene-butadiene, orstyrene-propylene-diene rubber.
 14. The ball of claim 1 , wherein thecenter is a solid center, wherein the solid center comprises a resilientpolymer component.
 15. The ball of claim 14 , wherein the solid centercomprises polybutadiene, natural rubber, polyisoprene,styrene-butadiene, or styrene-propylene-diene rubber.
 16. The ball ofclaim 13 , wherein the resilient polymer component comprises1,4-cis-polybutadiene having a molecular weight average of about 50,000to 1,000,000.
 17. The ball of claim 13 , wherein the amount of resilientpolymer component is between about 60 to 99 weight percent of the totalweight of polymer components.
 18. The ball of claim 13 , furthercomprising at least one of a filler, a free-radical initiator, or acrosslinking agent.
 19. The ball of claim 13 , wherein the mantle layerhas a flexural modulus of greater than about 3.5 MPa.
 20. The ball ofclaim 1 , wherein the soft intermediate layer is comprised of a naturalor a synthetic latex material.
 21. The ball of claim 1 , wherein theintermediate layer is comprised of additives, fillers, thickeners, or acombination thereof.
 22. The ball of claim 1 , wherein the filler iszinc oxide and is present in an amount of about 0.5 to 20 weightpercent.
 23. A golf ball comprising: a solid center having a firsthardness; an intermediate layer formed over the solid center having asecond hardness less than the first; an outer layer formed over theintermediate layer having a third hardness greater than the firsthardness; a cover.
 24. The ball of claim 23 , wherein the first hardnessis from about 20 to 40 Shore D.
 25. The ball of claim 23 , wherein thesecond hardness is less than about 20 Shore D.
 26. The ball of claim 23, wherein the third hardness is greater than about 50 Shore D.
 27. Amulti-layer golf ball comprising: a core having at least one layer; acover disposed concentrically about the core and having at least onelayer; and an intermediate layer formed of a responsive viscoelasticcomposition disposed between the core and the at least one cover layer.28. The golf ball of claim 27 , wherein the intermediate layer is lessthan about 0.01 inches thick.
 29. The golf ball of claim 27 , whereinthe intermediate layer is from about 0.0005 to 0.01 inches thick. 30.The golf ball of claim 27 , wherein the intermediate layer is from about0.0008 to 0.002 inches thick.
 31. The golf ball of claim 27 , whereinthe intermediate layer is from about 0.01 to 0.1 inches thick.
 32. Thegolf ball of claim 27 , wherein the intermediate layer is from about0.01 to 0.03 inches thick.
 33. The golf ball of claim 27 , wherein theintermediate layer is disposed between two cover layers.
 34. The golfball of claim 27 , wherein the intermediate layer is disposed betweenthe core and a second intermediate layer.
 35. The golf ball of claim 27, wherein the intermediate layer has a plasticity of about 20 mils to150 mils.
 36. The golf ball of claim 27 , wherein the intermediate layerhas a plasticity of about 60 mils to 120 mils.
 37. The golf ball ofclaim 27 , wherein the intermediate layer comprises a solid, semi-solid,gel, or gel-like material.
 38. The golf ball of claim 37 , wherein thematerial comprises at least one of polydimethyl siloxane, dimethylcyclosiloxane, a hydroxy-terminated polydimethyl siloxane, polyvinylalcohol, an acrylic plastisol, an acrylic organosol, a hydrocarbon-basedgel, a sulfonate ionomer, butyl rubber ionomer, an ionized crosslinkedpolyacrylamide gel, a microporous fast-response gel, a thermoplasticelastomer gel, or a blend thereof.
 39. The golf ball of claim 27 ,wherein the intermediate layer material has a hardness of less thanabout 90 Shore A.
 40. The golf ball of claim 27 , wherein theintermediate layer material has a hardness of less than about 70 ShoreA.
 41. The golf ball of claim 27 , wherein the cover has a thickness ofabout 0.02 to 0.1 inches.